Rise in body temperature helps fish swim faster

Washington: A new study finds that a rise in body temperature enables certain species of fish to maximize their swimming distance and speed.

Some species of fish possess a unique physiological characteristic -- a web of arteries and veins lying very close together -- that enables them to raise their internal temperatures higher than that of the water surrounding them.

Certain species including some sharks and tunas possessing the ability to warm their core -- a process called endothermy -- are able to swim two and a half times faster than those whose body temperature doesn't change.

These species can also swim twice as far -- ranges comparable to those of warm-blooded animals such as penguins and other marine mammals.

"The cost of moving faster and farther is high so there has to be an ecological reason that outweighs the physiological expenditure," said Jenn Caselle, biologist at the University of California, Santa Barbara.

"These endothermic fishes are putting a lot more energy into each unit of movement than their cold-blooded counterparts are," Caselle noted.

For the study, the team combined existing data with new information they obtained by attaching sensors to several sharks in different locations around the world.

The researchers' analysis suggests that warmer "red" muscle endothermy permits speedier cruising and greater endurance, which in turn enables these fishes to swim long distances relatively quickly.

This characteristic allows the fishes to take advantage of seasonally variable food sources.

Endothermy evolved independently in these distinctly different groups of fishes, noted the study.

The two taxonomic groups diverged more than 450 million years ago, and their common ancestor was most likely cold-blooded.

"This research begins to shed light on possible reasons why these endothermic fish evolved in this way," Caselle concluded.

The study appeared in the Proceedings of the National Academy of Sciences.